# std::insert_iterator

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< cpp‎ | iterator

Defined in header `<iterator>` |  |
template< class Container > class insert_iterator : public std::iterator<std::output_iterator_tag, void, void, void, void> |  | (until C++17)
template< class Container > class insert_iterator; |  | (since C++17)

`std::insert_iterator` is a LegacyOutputIterator that inserts elements into a container for which it was constructed, at the position pointed to by the supplied iterator. The container's `insert()` member function is called whenever the iterator (whether dereferenced or not) is assigned to. Incrementing the `std::insert_iterator` is a no-op.

### Member types

Member type | Definition
`iterator_category` | std::output_iterator_tag
`value_type` | void
`difference_type` |
void | (until C++20)
std::ptrdiff_t | (since C++20)
`pointer` | void
`reference` | void
`container_type` | `Container`

Member types `iterator_category`, `value_type`, `difference_type`, `pointer` and `reference` are required to be obtained by inheriting from std::iterator<std::output_iterator_tag, void, void, void, void>. | (until C++17)

### Member functions

(constructor) | constructs a new `insert_iterator` (public member function)
operator= | inserts an object into the associated container (public member function)
operator* | no-op (public member function)
operator++operator++(int) | no-op (public member function)

### Member objects

Member name | Definition
`container` (protected member object) | a pointer of type `Container*`
`iter` (protected member object) | an iterator of type `Container::iterator`(until C++20) `ranges::iterator_t<Container>`(since C++20)

### Example

Run this code

    #include <algorithm>
    #include <iostream>
    #include <iterator>
    #include <list>
    #include <vector>

    int main()
    {
        std::vector<int> v{1, 2, 3, 4, 5};
        std::list<int> l{-1, -2, -3};
        std::copy(v.begin(), v.end(), // may be simplified with std::inserter
                  std::insert_iterator<std::list<int>>(l, std::next(l.begin())));
        for (int n : l)
            std::cout << n << ' ';
        std::cout << '\n';
    }

Output:

    -1 1 2 3 4 5 -2 -3

### See also

inserter | creates a std::insert_iterator of type inferred from the argument (function template)
back_insert_iterator | iterator adaptor for insertion at the end of a container (class template)
front_insert_iterator | iterator adaptor for insertion at the front of a container (class template)

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